【明報專訊】I am writing this as the police pursue a man with a gun who was involved in a shooting nearby. You can hear the whirring of a helicopter and the sirens of police cars from a distance. All tests and activities have been cancelled or postponed, and I am taking shelter in my room with the door locked. Just a few days ago, Cornell, Columbia, Brown and Yale Universities received bomb and gun threats via phone calls and tweets, along with other institutions. Buildings were evacuated for hours while various police departments swept them with bomb detection dogs.